The present invention relates to a method and apparatus for the extermination of subterranean burrowing air-breathing animals, such as ants, moles, gophers, etc.
Numerous attempts have been made to provide non-toxic methods of exterminating obnoxious burrowing animals which do not at the same time result in the extermination of beneficial adjacent animals, such as earthworms. For instance, U.S. Pat. No. 4,597,217 discloses a method of suffocating field mice in their underground burrows. Liquid nitrogen is poured into the burrow and then evaporates to fill the burrow with gaseous nitrogen, causing the suffocation of any field mouse in the burrow. An enclosure is placed over one of the burrow exits so as to require the evaporated nitrogen to be forced to another burrow exit for escape. However, if the subterranean burrow network is extensive, with many different levels therein, the evaporated nitrogen (being less dense than ambient air) will diffuse upwardly and follow the most direct path to escape from the remote burrow exit, thereby possibly bypassing a substantial portion of the subterranean burrow network. U.S. Pat. No. 4,640,044 discloses a transparent hood or cover which is placed over an ant mound, thereby raising the temperature within the mound sufficiently to kill the ants within the nest. A lens may be provided within the hood to intensify the greenhouse-effect heating therein. While this invention will undoubtedly result in extremely high temperatures in the upper portions of an ant mound, it will have relatively little effect on ants within the subterranean burrows located a number of feet beneath the earth's surface.
U.S. Pat. No. 4,637,161 discloses a steam-injection means for injecting steam into the underground habitat of insects or burrowing animals. A tubular ground probe is inserted into the burrow, with a downwardly opening shield to maintain the steam under ground. Vents are provided on the shield to vent steam escaping from the ground around the probe. Steam may be injected at different depths simultaneously. Likewise, U.S. Pat. No. 4,667,436 discloses an apparatus having a probe which is inserted into an ant mound. Electric current is directed through the probe so as to electrocute ants within the mound.
U.S. Pat. No. 3,029,558 discloses a method of soil fumigation wherein a fumigating blanket is placed over a quantity of soil and a fumigating gas is introduced thereunder so as to kill objectionable weeds or insects. Lastly, U.S. Pat. Nos. 3,685,431 and 1,948,228 both disclose methods of killing insects which infest machinery used in the manufacture of grain products. In the '431 patent, grain (and entrained insects) are directed over electrified grids, electrocuting insects therein. A non-explosive atmosphere of inert gas (such as CO.sub.2) is introduced
into the system to prevent combustion. In the '228 patent, a non-poisonous gas (such as air) is heated to a temperature (at least 130.degree. F. and preferably 200.degree. F.) sufficient to destroy insects in any stage of life contained either in the grain or the machinery.